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From the department of "everything you need to know you learned in kindergarten," it is good to share. It can even be good for business. But sharing your wireless Internet access out-of-the-box can leave your network vulnerable and without any controls over user activity.

Whether you want to share with family, neighbors, co-workers, or customers, a wireless hotspot can give you say over how and when your wireless access is used. You can also use the opportunity to promote products or services to guests of your wireless system or, in some setups, even bill them for their usage.

Any wireless router will typically "share" your Internet connection with nearby wireless users, but if you want to regulate sharing, you need a hotspot. One way to create a hotspot is by using the powerful, free, and open source DD-WRT firmware loaded onto a compatible router, such as the Linksys WRT54G.

Version alert

Although DD-WRT provides lots of advanced features for a consumer-grade router, it can be confusing to select a version. Officially, the latest stable release is V23 SP2, released in 2006. V24 development is well-along, and many beta and RC versions are already available.

Unfortunately, one quirk of DD-WRT development is that new does not always mean better, at least not during development cycles. When it comes to hotspots, experience suggests that V23 SP2 is the most usable version, because some hotspot features do not work reliably in newer V24 releases. Hopefully this will be fixed when a stable V24 release is made available in the future. This tutorial is written for a router running DD-WRT V23 SP2.

Hotspot horticulture

Many hotspots are known as "captive portals." You've probably used a captive portal at your local coffee shop or while staying at a hotel. After associating with the wireless network, you try to connect to a Web site but are redirected to a wireless "landing" page hosted by the hotspot owner.

From here, several things can happen. The simplest kind of captive portal will simply display information about your hotspot owner, like "Welcome to the Coffee Cafe!", perhaps with some advertising. There will be a button to connect, which authorizes you to freely browse the Web.

A more sophisticated captive portal may enforce some usage policies on the guest, such as connect time. A cafe, for example, might want to discourage visitors from buying a $1 coffee and then surfing the Web for three hours. One popular approach is to charge more than $1 for a coffee. Another is to limit guest access to, say, 60 minutes, which is done using a suitable captive portal server.

The most advanced captive portals can enforce a wider range of policies, such as connection speed and transfer limits, plus billing systems like those commonly found in chain hotels, restaurants, and airports.